An adult female black bear that repeatedly treed hikers and ravaged their backpacks for food has been killed by rangers, who said their efforts to reform the bear had failed.

"Our first responsibility is to protect human life," Yellowstone spokeswoman Joan Anzelmo said. "In the last four seasons we tried a variety of methods to help the bear change its habits."The bear frequently approached back country hikers in the Heart Lake region, took their packs, occupied back country camps and punctured containers in search of food, she said. The sow actively sought out people to locate human foods, often during daylight, she added.

She said park managers tried other methods to rid the bear of its people- and food-conditioned habits. Back country areas involved were intermittently closed or party size was restricted, she said.

Unsuccessful attempts were made in 1986 and 1987 to destroy the bear, Anzelmo said, but rangers succeeded Saturday when the bear was found on the north shore of Heart Lake in the southern part of the park.

The last bear destroyed by park officials was an adult female grizzly in October 1987. Officials said at the time the 19-year-old grizzly sow, No. 83, had a history of trouble in Yellowstone, was habituated to human food and posed a danger for people.